Reinforced molded implant formed of cortical bone

ABSTRACT

This invention relates to arthodesis for stabilizing the spine. More specifically, the present invention is directed to an intervertebral spacer formed of a bone material and to methods of treating patients having spinal deformities. The invention provides a spinal implant assembly comprising bone-derived components. The bone-derived components can be formed into modular units that can be assembled to provide a wide variety of implant configurations. In addition, the bone-derived components can form scaffold that can withstand the shear and impact forces necessary to insert the assembled implant into a disc space between adjacent vertebrae. In preferred forms the implants define an open spacer that serves as a depot for receipt of an osteoconductive material. The ostoegenic material is preferably a moldable filler that can form a molded reinforced implant.

BACKGROUND OF THE INVENTION

The present invention relates to arthodesis for stabilizing the spine.More specifically, the present invention is directed to anintervertebral spacer formed of a bone material and to methods oftreating patients having spinal deformities.

Removal of damaged or diseased discs and restoration of disc spaceheight to treat chronic back pain and other ailments are known medicaltechniques. Implants such as intervertebral spacers are often implantedin the disc space to maintain or reestablish disc space height afterremoval of all or a portion of the disc. The spacers can be formed of avariety of both resorbable and non-resorbable materials, including, forexample, titanium, surgical steel, polymers, composites, and bone. It isalso often desirable to promote fusion between the vertebral bodies thatare adjacent to the damaged or diseased discs. Typically an osteogenicmaterial is combined with a spacer and inserted in the disc space tofacilitate and promote bone growth. While the selection of the implantconfiguration and composition can depend upon a variety ofconsiderations, for arthodesis it is often desirable to select aresorbable material than does not stress shield the bone ingrowth. Boneand bone-derived components can provide suitable material to prepare theimplants. However, bone material acceptable for use in implants is ascarce resource, being derived from limited human tissue donorresources.

Suitable bone or bone-derived material for use in implants, in general,is almost exclusively obtained from allograft and xenograft sources,both which are precious resources. Since intervertebral spacers mustwithstand the compressive loads exerted by the spine, these implants areoften formed from cortical long bones, which are primarily found in thelower limbs and include, for example, femur, fibula, and the tibiabones. The long bones make up only a fraction of the available bonesource. Thus, sources of bone suitable for structural intervertebralspacers are extremely limited. The scarcity of desired donor bone makesit difficult to provide implants having the desired size andconfiguration for implantation between adjacent lumbar vertebrae, whichcan require relatively large implants. It is further anticipated that asthe population ages there will be an increased need for correction forspinal deformities and a concomitant increase in the demand forbone-derived components. Therefore, these structural bone portions mustbe conserved and used efficiently to provide implants. The scarcity ofsuitable bone material has also hindered efforts to design andmanufacture varying configurations of suitable implants for arthodesisof the spine. Further, various implant configurations have not beenphysiologically possible to obtain given the structural and geometricalconstraints of available donor bone.

In light of the above-described problems, there continues to be a needto provide suitable implants to facilitate patient treatment. Thepresent invention addresses this need and provides a variety of otherbenefits and advantages.

SUMMARY OF THE INVENTION

The present invention relates to spinal implants, the manufacture anduse thereof. Various aspects of the invention are novel, nonobvious, andprovide various advantages. While the actual nature of the inventioncovered herein can only be determined with reference to the claimsappended hereto, certain forms and features, which are characteristic ofthe preferred embodiments disclosed herein, are described briefly asfollows.

In one form, the invention provides an implant for promoting bone fusionbetween adjacent vertebral bodies. The implant has a longitudinal axisand comprises an assembly of cortical bone-derived components. Thecomponents are comprised of a first strut having a first bone-engagingportion and an opposite second bone-engaging portion. A first impactsurface is disposed between the first bone-engaging portion and thesecond bone-engaging portions. The bone-derived components also includea second strut spaced from the first strut. The second strut has a thirdbone-engaging portion and an opposite fourth bone-engaging portion. Asecond impact surface is disposed between the third and fourthbone-engaging portions. The components also include an elongatecross-member that extends from the first strut to the second strut. Thesecond strut in cooperation with the first strut defines an internalspace. In one embodiment the implant can be provided as an open cage. Anosteogenic material can be combined with the implant. The osteogenicmaterial can be interposed between the first and second strut.Preferably, the osteogenic material is provided to be formed within theinternal space and/or adherent to at least one of a first strut, thesecond strut, and the cross-member. The osteogenic material can also beadapted to be moldable to provide a semi-rigid shaped component.

In alternative forms, the first and second strut can be defined bysubstantially planar walls that can be adapted to restore normal discheight and/or provide correct lordosis of the spine. The first andsecond strut can include opposite bone-engaging portions that areseparated from each other at a first end of the strut by a distance D₁and wherein the opposite bone-engaging uniformly taper to a seconddistance D₂ at a second end of the strut, such that D₁ is greater thanD₂. Alternatively, the bone-engaging portions can define an arcuatesurface wherein the opposite bone engaging portions separate from eachother at a maximum distance at a point located between the first and thesecond end on the respective strut. In still yet other embodiments, thefirst and second struts can define curved wall portions that approximatethe medullary canal of a long bone.

In another form, the present invention provides an implant for promotingbone fusion. The implant has a longitudinal axis and comprises anassembly of cortical bone-derived components. The components comprise afirst strut having a first bone-engaging portion and an opposite secondbone-engaging portion. The first strut also includes a first slot formedtherein and extending from the first bone-engaging portion. The firstslot has a first internal wall portion and opposing second internal wallportion and an internal end wall portion therebetween. The implantassembly also comprises a second strut that has a third bone-engagingportion and an opposite fourth bone-engaging portion. The second strutalso has a second slot formed therein and extending from the thirdbone-engaging portion. The second slot includes a first internal wallportion and opposing second internal wall portion and internal end wallportion therebetween. The first slot is adapted to receive a portion ofthe second strut, and the second slot on the second strut is adapted toreceive a portion of the first strut to interengage the first and secondstrut to form the implant assembly. When thus configured, the implantcan be adapted to be inserted in the intervertebral space or,alternatively, the implant can be sized to provide a replacement for avertebral body.

The present invention also provides a method of treating a spinaldeformity. The method comprises surgically preparing a intervertebralspace between adjacent endplates of adjacent vertebrae and inserting animplant into the prepared space. The implant comprises a first struthaving a first bone-engaging portion, an opposite second bone-engagingportion and a first impact surface disposed therebetween, a second strutspaced from said first strut, said second strut having a thirdbone-engaging portion, an opposite fourth bone-engaging portion, and asecond impact surface disposed therebetween, said second strut incooperation with said first strut defining an internal space, and across-member extending from the first strut to the second strut into theintervertebral space.

In yet another form the present invention provides other methods fortreating spinal deformities. These methods include surgically preparinga patient to receive a spinal implant; and implanting an implantcomprising of an assembly of cortical bone-derived components. Thecortical bone-derived components include: a first strut having a firstbone-engaging portion and a opposite second bone-engaging portion, saidfirst strut having first slot formed therein, and a second strut havinga third bone-engaging portion and a opposite fourth bone-engagingportion, said second strut interengaging said first strut to form theimplant.

Further objects, features, aspects, forms, advantages and benefits shallbecome apparent from the description and drawings contained herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of one embodiment of an implant assembly accordingto the present invention.

FIG. 2 is an exploded view of the implant assembly illustrated in FIG.1.

FIG. 3 is an elevated end view of a lordotic implant assembly includingan osteogenic material.

FIG. 4 is a perspective view of the implant assembly depicted in FIG. 3.

FIG. 5 is a perspective view of an alternate embodiment of an implantassembly including an osteogenic material for use in the presentinvention.

FIG. 6 is an anterior view of adjacent vertebrae illustrating thebi-lateral placement of a pair of implant assemblies provided inaccordance with the present invention.

FIG. 7 is a top view of a vertebral body illustrating the bi-lateralplacement of a pair of implant assemblies provided in accordance withthe present invention.

FIG. 8 is a perspective view of one embodiment of an implant assemblyhaving three substantially parallel struts provided in accordance withthe present invention.

FIG. 9 is an elevated end view of the implant assembly illustrated inFIG. 8.

FIG. 10 is a perspective view of an implant embedded in a matrix ofosteogenic material.

FIG. 11 is a perspective view of one embodiment of a lordotic implantassembly for use in the present invention.

FIG. 12 is a perspective view of one embodiment of a domed implantassembly, for use with the present invention.

FIG. 13 is an anterior view of two adjacent vertebrae illustrating theplacement of a domed implant assembly depicted in FIG. 12.

FIG. 14 is a perspective view of another embodiment of an implantassembly for use according to the present invention.

FIG. 15 is a top view of the implant assembly depicted in FIG. 14.

FIG. 16 is an exploded view of the implant assembly depicted in FIG. 14.

FIG. 17 is a top view of one embodiment of an implant assembly havingcurved struts for use in the present invention.

FIG. 18 is an elevated end view of the implant assembly depicted in FIG.17.

FIG. 19 is a top view of the implant assembly depicted in FIG. 17positioned on a superior endplate of a lumbar vertebra.

FIG. 20 is an exploded, partial view of an implant assembly of thepresent invention illustrating a dovetail connection of a cross-memberand a strut.

FIG. 21 is an exploded, partial view an implant assembly of the presentinvention illustrating a threaded connection of a cross-member and astrut.

FIG. 22 is a partial sectional view of an implant assembly of thepresent invention illustrating a cross-member engaged to a strut using akeeper.

FIG. 23 is an exploded view of an alternative embodiment of an implantassembly having a single, planar cross-member.

FIG. 24 is a partial sectional view of an alternative embodiment of animplant assembly of the present invention illustrating a cross-memberengaged to a strut using a retaining ring.

FIG. 25 is an elevated end view of the implant assembly depicted in FIG.23.

FIG. 26 is a schematic illustrating the selection of a bone portion froma cross-section of a femur.

DETAILED DESCRIPTION OF THE INVENTION

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiments illustratedherein and specific language will be used to describe the same. It willnevertheless be understood that no limitation of the scope of theinvention is thereby intended. Any alterations and further modificationsin the described implants or methods, and any further applications ofthe principles of the invention as described herein, are contemplated aswould normally occur to one skilled in the art to which the inventionrelates.

The present invention provides a spinal implant that can be assembledfrom individual bone-derived components. In one form, the individualcomponents can be relatively small, and yet the assembled bone implantcan be a larger structure exhibiting suitable strength to withstand thecompression loading exerted by a spinal column. The components can bederived from donor bone, such as cortical allograft bone. In addition,the components can be formed as modular pieces having uniform size andshape to facilitate manufacture of the spinal implants. For example, theimplant can be provided in selected dimensions and configurations tomaintain disc height, correct lordosis, kyphosis or other spinaldeformities. In other forms, the spinal implant provides a boneconstruct that can serve as reinforcing scaffolding for a variety ofosteogenic materials to facilitate bone fusion. Thus, this inventionprovides efficient use of the precious donor bone material and yetallows for the manufacture of a wide variety of implant configurations.

FIG. 1 is a plan view of one embodiment of a spinal implant 10 for usein the present invention. Implant 10 defines a longitudinal axis 11 andincludes a first strut 12, a second strut 14 spaced from first strut 12,and cross-member 16 extending therebetween. First strut 12 and secondstrut 14 are each positioned to lie in a plane substantially parallel tolongitudinal axis 11. Implant 10 includes at least one additionalcross-member 16A connecting first strut 12 and second strut 14. It isunderstood that in alternative embodiments implant 10 can have one or aplurality of cross-members connecting first strut 12 to second strut 14.

Referring additionally to FIG. 2, which is an exploded view of theimplant assembly 10 depicted in FIG. 1, first strut 12 is illustrated ashaving a substantially rectangular configuration.

First strut 12 includes a first bone-engaging portion 20 and an oppositesecond bone-engaging portion 22 spaced from the first bone-engagingportion 20 by a first distance illustrated by reference line 21, andwhich can be selected to be equal to D₁. First bone-engaging portion 20and second bone-engaging portion 22 can be provided to includeanti-retropulsion structures 28. In the illustrated embodiment, firstbone-engaging portion 20 is provided with a plurality of notches 28formed therein. Notches 28 provide a mechanical interlock with theadjacent vertebral bone endplates and prevent retropulsion of theimplant from the intervertebral space. First bone-engaging portionand/or second bone-engaging portion can also be configured with ridges,spikes, and the like to inhibit retropulsion from the disc space.Alternatively, first bone-engaging portion 20 and second bone-engagingportion 22 can be provided as a substantially smooth or uniformly linearsurface. It is understood by those skilled in the art that the exactconfiguration of first strut 12 can be provided in a variety ofconfigurations, which can be selected to impart a desired correctiveeffect on a spinal column or portion thereof.

Second strut 14 can be provided substantially as described for firststrut 12. Second strut 14 includes a third bone-engaging portion 24, anopposite fourth bone-engaging portion 26. Second strut 14 can includethe same structural components as described for first strut 12,including anti-retropulsion structures 28. Third bone-engaging portion24 is spaced from fourth bone-engaging portion 26 by a second distancerepresented by reference line 23, which can be selected to be D₂. In theillustrated embodiment for implant 10, D₁ is substantially equal to theD₂. In alternative embodiments, the first distance does not have toequal the second D₂. Thus, D₁ and D₂ individually can be selected torestore and/or maintain desired disc space height between adjacentvertebrae including cervical, thoracic and lumbar vertebrae. Preferably,D₁ and D₂ are selected to range between about 5 mm and about 20 mm. Morepreferably, D₁ and D₂ are selected to range between about 10 mm andabout 15 mm.

Second strut 14 is spaced from first strut 12. The distance second strut14 is spaced from first strut 12 can be varied depending upon thedesired use and/or desired site for implantation of the resultingimplant assembly. For example, second strut 14 can be spaced from firststrut 12 to provide a single implant assembly that is sized tosubstantially extend the lateral width of a disc space. Alternatively,implant 10 can be sized to allow the bi-lateral placement of a pair ofimplants within the disc space as illustrated in FIG. 7.

First strut 12 includes impact surface 25 positioned substantiallyorthogonal to longitudinal axis 11. The impact surface can be disposedbetween first bone-engaging portion 20 and second bone-engaging portion22. Similarly second strut 14 includes impact surface 27 also positionedsubstantially orthogonal to longitudinal axis 11. Impact surfaces 25 and27 can define a thickened wall portion of struts 12 and 14. Impactsurfaces 25 and 27 are adapted to withstand impact forces necessary todrive implant 10 into a disc space. Further, impact surface 25 and 27can be provided with a surface to facilitate driving implant 10 into adisc space. For example, surfaces 25 and 27 can be roughened, knurled orridged to maintain static contact between an insertion tool (not shown)and implant 10.

First strut 12 terminates in a first end 32 and at an opposite secondend 34. Similarly, second strut 14 terminates at a first end 33 and atan opposite second end 35. In one form, first ends 32 and 33 defineimpact surfaces 25 and 27, respectively. Further, first ends 32 and 33are configured to include tool engaging apertures 30 to engagecounterpart structures on implant holders and/or insertion tools (notshown). Apertures 30 can include a uniformly smooth bore, a tapered boreor, alternatively, a threaded bore portion. Preferably, tool-engagingportions 30 facilitate insertion of the implant into the disc space andinhibit lateral movement of the implant during insertion. In theillustrated embodiment, second ends 34 and 35 include curved surfaces29, 31, respectively, to facilitate and ease insertion of implant 10into the disc space.

In a preferred form, first strut 12 and second strut 14 can be providedas modular units that can be coupled via at least one cross-member. Themodular units can be obtained by uniform cutting and machining of donorbone. Further, the donor bone can be bone remnants obtained aftermanufacture of implant configurations as illustrated in FIG. 26 anddiscussed more fully below. This provides efficient use of preciousdonor bone resources. The modular units can be of preselectedconfiguration and dimensions. Preferably struts 12 and 14 are providedin configurations to facilitate bone fusion and provide correctlordosis, kyphosis and other spinal deformities.

In the illustrated embodiment, cross-member 16 and cross-member 16Aextend from first strut 12 through interior area 19 to second strut 14.In alternative embodiments, cross-members 16 and/or, 16A can be engagedto first strut 12 and second strut 14 about their respective periphery,for example, proximal to first ends 32 and 33 or to second ends 33 and35. When cross-member 16 or 16A is positioned proximal to first ends 32and 33, the cross-members can also be adjacent impact surfaces 25 and27, respectively.

Cross-member 16 includes a proximal end 36, which is capable of engagingfirst strut 12. In the illustrated embodiment, proximal end 36 engagesin aperture 38 of first strut 12. Cross-member 16 also includes a distalend 37, which is capable of engaging with strut 14 via aperture 39.Similarly, cross-member 16A includes a proximal end 36A and a distal end37A. Proximal end 36A is provided to engage first strut 12, and distalend 37A is provided to engage strut 14. Cross-member 16 and secondcross-member 16A are adapted to engage in first strut 42 and secondstrut 14 to provide an assembled implant that is capable of withstandingthe shear and impact forces needed to drive the implant assembly intothe intervertebral space. Cross-member 16 is illustrated as acylindrical rod. In alternative forms, cross-member 16 can be configuredas a shaft having a square, rectangular, triangular or ovoidcross-section. Further, it will be understood by those skilled in theart that cross-members 16 and 16A are adapted to engage a first andsecond strut 12 and 14, respectively, in a variety of configurations,which are discussed in more detail below.

Implant 10 can be configured as an open cage vertebral implant. The opencage vertebral implant provides a depot for receipt of anosteoconductive/inductive filler. Further, when the implant includes afiller and is sized to be received within a prepared disc space, implant10 provides structural support to maintain disc height yet allow broadsurface area and intimate contact between the filler and bone tissue ofthe vertebral end plates.

FIGS. 3 and 4 are illustrations of implant assembly 40 including anosteogenic material 48. Implant assembly 40 includes a first strut 42,second strut 44 and cross-members 46 and 47. First strut 42 and secondstrut 44 define an interior space 49 therebetween. First strut 42includes a first bone-engaging portion 50, an opposite bone-engagingportion 52, and a first impact surface 55 therebetween. Similarly,second strut 44 includes a third bone-engaging portion 54, an oppositefourth bone-engaging portion 56, and a second impact surface 57therebetween. First strut 42 and second strut 14 includeanti-retropulsion structures 58 formed therein. In the illustratedembodiment, osteogenic material 48 is deposited between a first strut 42and second strut 44, substantially filling the entire interior space 49.The osteogenic material 48 can be provided as a moldable material thatadheres to the scaffolding defined by struts 42, 44 and optionallycross-members 46 and 47. Osteogenic material 48 also can be provided insufficient amounts and in a form to extend beyond first and thirdbone-engaging portions 50 and 54, respectively, and/or second and fourthbone-engaging portions 52 and 56, respectively. Preferably thecompressed osteogenic material can bear a portion of the load exerted onthe implant assembly 40 by the spinal column. In alternativeembodiments, first strut 42 and second strut 44 can be substantiallysurrounded or embedded in an osteogenic material so the osteogenicmaterial substantially surrounds struts 42 and 44.

First strut 42 includes a first end 60 and an opposite second end 62.First bone-engaging portion 50 is spaced from second bone-engagingportion 52 proximate to first end 60 by first distance illustrated byreference line 41, which can be selected to equal D₁. Similarly, firstbone-engaging portion 50 is separated from second bone-engaging portion52 proximal to second end 62 by a third distance, which can be selectedto equal D₃ (not shown). Second strut 44 includes a first end 64 and anopposite second end 66. Third bone-engaging portion 54 is separated fromfourth bone-engaging portion 56 proximal to first end 64 by a seconddistance illustrated by reference line 45, which can be selected toequal D₂. Similarly, third bone-engaging portion 54 is separated fromfourth bone-engaging portion 56 proximal to second end 66 by a fourthdistance illustrated by reference line 67, which can be selected toequal D₄. The values for D₁, D₂, D₂ and D₄ can be individually selectedto provide an implant assembly capable of achieving a desired orthopedicresult.

In one form, first strut 42 has a height adjacent to first end 60defined by distance D₁ and a height adjacent to second end 62 defined byD₃. Preferably, but not required, when so provided, first strut 12tapers uniformly from the height D₁ adjacent first end 60 to the heightD₃ adjacent second end 62. Similarly, second strut 44 can be configuredto have a height adjacent to first end 64 defined by D₂ and a heightadjacent to second end 66 defined by D₄ smaller than D₂. Second strutcan also be provided to uniformly taper in height from first end 64 tosecond end 66. Further in selected forms D₂ can be selected to be lessthan D₁, and D₄ can be selected to be less than D₃.

FIG. 5 is a perspective view of an implant assembly 70. Implant assembly70 is illustrated as an elongate spacer defining a longitudinal axis 71and including a first strut 72, a second strut 74 and an osteogenicmaterial 76 interposed therebetween. First strut 72 includes a firstbone-engaging portion 73, an opposite second bone-engaging portion 75,and a first impact surface 77 positioned therebetween. Second strut 74includes a third bone engaging portion 78 and an opposite fourthbone-engaging portion 79 and impact surface 84 disposed therebetween.Opposite bone-engaging portions extend from a first end 85 to a secondend 86 on strut 74. First bone-engaging portion 73 includes an arcuateedge 80 extending substantially parallel to longitudinal axis 71, andthird bone-engaging portion 78 includes second arcuate edge 81 extendingsubstantially parallel to longitudinal axis 71. Similarly, secondbone-engaging portion 75 and fourth bone-engaging portion 79 also, butare not required to, include arcuate edges (not shown). The first andsecond struts include pairs of opposite bone-engaging portions, 73, 75,78 and 79 that are separated from each other at a maximum distance at apoint between the first and second ends of the respective struts.

FIG. 6 is an anterior view of adjacent vertebrae illustrating thebi-lateral placement of a pair of implants according to the presentinvention. Implants 90A and 90B are inserted substantially parallel toeach other into an intervertebral space 100. Referring to implant 90A,it can be seen that first strut 92 includes first bone-engaging portion110 which bears against vertebral endplate 103 and an oppositebone-engaging portion 112 bearing against second vertebral endplate 105and a first end 96 extending therebetween. Implant 90A also includessecond strut 94, similar to first strut 92, includes a thirdbone-engaging portion 114 and an opposite fourth bone-engaging portion116 and a first end 98 extending therebetween. Each bone-engagingportion 114 and 116, respectively, bear against respective vertebralendplates 105 and 103. An osteogenic material 118 is interposed betweenfirst strut 92 and second strut 94. Osteogenic material 118 bearsagainst first and second endplates 103 and 105.

Implant 90A includes a first impact surface 89 formed in first end 96disposed between first bone-engaging portion 110 and an oppositebone-engaging portion 112 Second strut 94 includes a second impactsurface 91 formed in first end 98 disposed between third bone-engagingportion 114 and an opposite fourth bone-engaging portion 116. Impactsurfaces 89 and 91 are provided to withstand the shear and forcenecessary to impact the respective implants into the disc space. Forexample impact surfaces 89 and 91 can defined thicken portions on firststrut 92 and second strut 94. In preferred embodiments, impact surfaces89 and 91 have sufficient thickness to withstand the impact forcenecessary to drive implant 90A into a intervertebral space with loss ofintegrity or deforming the molded implant configuration depicted byimplant 90A including osteogenic material interposed between first andsecond strut 92 and 94. Impact surfaces 89 and 91 can define toolengaging apertures 93 and 95, respectively. It is understood by thoseskilled in the art that in addition to, or in place of, apertures 93 and95, a variety of tool engaging structures can included in implant 90A,for example, slots, recessed areas, projections and additionalapertures.

It can be seen from the illustrated embodiment that the bi-lateralplacement of implants 90A and 90B can define an interior region 120. Inpreferred embodiments, interior region 120 can also be packed with afiller, such as an osteogenic material (not shown). The osteogenicmaterial that is implanted into interior pocket 120 can be the same orcan be different from the osteogenic material 118 provided or interposedbetween first and second struts 92 and 94. Similarly, after completediscectomy and appropriate bi-lateral placement of implants 90A and 90B,additional cavities 122 and 124 lateral of respective implants 90A and90B can be provided to receive additional osteogenic material. Thisadditional osteogenic material may be the same or may be different fromthe osteogenic material 118 interposed between first strut 92 and secondstrut 94.

FIG. 7 is a top view looking down on the superior endplate of vertebra102 and implants 90A and 90B depicted in FIG. 6. Implant 90A is insertedfrom an anterior approach. First strut 92 has a second end 97 and secondstrut 94 has a second end 99, and each can include curved portions toease the impact force necessary to embed the implant in theintervertebral space. Thus, first ends 96 and 98 are positionedanteriorly on vertebra 102, and second ends 97 and 99 are positionedposteriorly on vertebra 102. In alternative embodiments, when implants90A and 90B are inserted from the posterior direction, second ends 97and 98 can be provided similarly as discussed for first ends 96 and 98to ease insertion of the implant in the anterior direction.

FIGS. 8 and 9 illustrate an alternative embodiment of an assembledimplant according to the present invention. Implant 130 includes a firststrut 132, a second strut 134 spaced from the first strut 432, and athird strut 136 spaced from the second strut 132. As with the previousimplants 10, 40, 60 and 90A and 90B, each of the struts 132, 134, and136 of implant assembly 130 include a pair of bone-engaging portionsopposite each other and impact surfaces disposed between the oppositebone-engaging portions. Further, implant 130 includes a firstcross-member 140 and a second cross-member 142 shown in dashed linesextending from strut 132 to strut 136. Cross-member 140 and/orcross-member 142 can be an integral cross-member extending from strut132 through strut 134 and to strut 136. Alternatively, cross-member 140and/or 142 can be an assembly of one or more cross-member sections. Thecross-member sections can be substantially co-linear through implant130. Alternatively, cross-member sections can be offset from each otheras they extend from first strut 132, second strut 134 and to third strut136. Implant 130 also includes a first internal area 144 defined byfirst strut 132 and second strut 134 and a second internal area 146defined by second strut 134 and third strut 136. In preferredembodiments, internal areas 144 and 146 are filled with an osteogenicmaterial 145. Preferably, this osteogenic material 145 is provided toadhere to the first strut, second strut, and/or third strut andcross-members 140 and 142. The osteogenic material will be discussed inmore detail below.

In the illustrated embodiment, first strut 132, second strut 134, thirdstrut 136 each include a first end 133, 135 and 137, respectively. Eachfirst end 133, 135 and 137 defines respective impact surfaces 139, 141and 143, respectively. First ends 133, 135 and 137 include one or moretool-engaging structures shown as apertures 138A, 138B and 138C. Inalternative embodiments, implant 130 is not required to include eitheror both impact surfaces or tool-engaging structures on each strut.Therefore, implant 130 can include an impact surface and/or atool-engaging structure in either of first strut 132, second strut 134and/or third strut 136. Preferably, at least two struts, for example,first strut 132 and third strut 137, include impact surfaces and/ortool-engaging apertures.

In preferred embodiments, implant 130 is configured to be receivedwithin the intervertebral space on adjacent vertebrae. Thus, implant 130can be provided in a variety of sizes, each size configured to beinserted between a specific pair of adjacent vertebrae, for example,cervical, thoracic, or lumbar vertebrae. Furthermore, the implantassembly 130 can be provided so that the distance between first strut132 and third strut 136, which is indicated by reference line 148, canbe selected to equal D₅. The value for D₅ can be selected to place aportion of first strut 132 and third strut 136 on the peripheral ringstructure apophysis of adjacent vertebrae.

FIG. 10 is an illustration of still another embodiment of an implantassembly according to the present invention. Implant assembly 160,similar to implant assembly 130, includes three struts 162, 164 and 166.Struts 162, 164 and 166 define internal areas 174 and 176. An osteogenicmaterial 178 can be received within internal areas 174 and 176.Furthermore, an osteogenic material 178 can be interposed between struts162 and 164, and 164 and 166; in addition, osteogenic material 178substantially encompasses first strut 162, second strut 164 and thirdstrut 166. Thus, the respective struts can be substantially encased inthe osteogenic material 178. In preferred embodiments, a portion of thefirst ends 163, 165 and 167 are available to engage an insertion tool.Therefore, in one embodiment, first ends 163, 165 and 167 extend beyondosteogenic material 178 to be available for attachment to an insertiontool (not shown).

FIG. 11 is a perspective illustration of another embodiment of alordotic implant assembly according to the present invention. Implantassembly 190 defines a longitudinal axis 191 and includes a first strut192, a second strut 194 and a third strut 196. Each of the respectivestruts 192, 194 and 196 include pairs of opposite bone-engaging portions210 and 212, 214 and 216, and 218 and 220, respectively.

First strut 192, second strut 194, and third strut 196 can be providedas modular components for the implant assembly. Thus, the struts 192,194 and 196 are provided in substantially the same configuration anddimensions. Therefore, opposing bone-engaging surfaces 210, 212, 214,216, 218 and 220 on each respective strut are separated by the samedistance. Further, each strut 192, 194 and 196 can be provided tocorrect lordotic deformities. For example, third strut 196 has a firstend 224 and a second end 228. Adjacent to first end 224, firstbone-engaging portion 218 and second bone-engaging portion 220 areseparated by a distance represented by reference line 222, which isselected to equal D₁. At second end 228, first bone-engaging portion 218is separated from second bone-engaging portion 220 by a distancerepresented by reference line 226, which is selected to equal D₃.Distance D₁ can be selected to be greater than D₃. In preferredembodiments, implant assembly 190 is provided to restore disc height andcorrect spinal lordosis.

FIG. 12 is an illustration of one embodiment of a domed implant assemblyaccording to the present invention. The implant assembly 240 defines alongitudinal axis 241. Implant assembly 240 includes a first strut 242,a second strut 244 and a third strut 246 extending in a directionsubstantially parallel to longitudinal axis 241. In the illustratedembodiment, first strut 242 and third strut 246 provide mirror images ofeach other. First strut 242 and third strut 246 are selected to have afirst height transverse to longitudinal axis 241 and illustrated byreference line 245. Preferably the first height is selected to provideand maintain desired disc space height. Second strut 244 is provided tohave a second height transverse to longitudinal axis 241 illustrated byreference line 243. In the illustrated embodiments, the first height isselected to be less than the second height. Preferably the first heightis between about 5 mm and about 20 mm; more preferably, between about 10mm to about 15 mm. The second height can be selected to be between about5 mm and about 25 mm; more preferably between about 10 mm and about 20mm.

As with the above-described implant assemblies, in implant 240, eachstrut 242, 244 and 246 includes opposite pairs of bone-engagingsurfaces. Further, the bone-engaging surfaces can be providedsubstantially as described for the bone-engaging surfaces of the aboveimplants 10, 40, 70, 90A, and 130.

Referring additionally to FIG. 13, which illustrates the insertion ofimplant 250 between adjacent vertebrae 252 and 254, it can readily beseen that struts 242, 244, and 246 engage in opposing endplates 256 and258 of vertebral bodies 252 and 254, respectively. First strut 242,second strut 244, and third strut 246 are illustrated as extendingthrough vertebral endplates 256, 258 and into the cancellous bonetissue. It is also considered to be within the scope of the presentinvention to provide first strut 242, second strut 244, and third strut246, which can be adapted to bear against opposing cortical boneendplates 256 and 258.

Implant 240 has a width transverse to longitudinal axis 241 andillustrated by reference line 247. Preferably the width is selected soimplant 120 extends laterally across the end plates of opposingvertebrae so a portion of first strut 242 and a portion of third strut246 engage the peripheral ring apophysis of the vertebrae.

FIGS. 14-16 illustrate an alternative embodiment of an implant assemblyaccording to the present invention. Implant assembly 260 includes atleast a first strut 262 and a second strut 264 substantially orthogonalto each other. Each strut 262 and 264 includes first bone-engagingportions 266 and 268, respectively, and opposite second bone-engagingportions 270 and 272, respectively. A moldable osteogenic material 271substantially encases struts 262 and 264.

In the illustrated embodiments, first strut 262 and 264 are adapted tomatingly interengage each other, as illustrated in FIG. 16. First strut262 includes a slot 274 extending from second bone-engaging portion 272.Slot 274 includes a first internal wall 276, an opposing second internalwall 278 and an end wall 280 disposed therebetween. Similarly, secondstrut 264 includes a slot 290 extending from first bone-engaging portion268. Slot 290 includes a first internal wall 282, an opposing secondinternal wall 284 and end wall 286 disposed therebetween. Whenassembled, slot 280 of first strut 262 receives a portion of secondstrut 264. Concomitantly, second slot 290 and second strut 264 receive aportion of first strut 262.

First strut 262 and second strut 264 can be obtained from slices ofcortical bone and exhibit a substantially rectangular shape having aheight defined by opposite bone-engaging portions 266, 272 and 268, 278of between about 5 mm to about 80 mm. In one form, implant assembly 260can be sized to be inserted in a disc space between adjacent vertebrae.The height of first strut 262 and second strut 264 can be selected to bebetween about 5 mm and about 20 mm. In another form, implant assembly260 can be sized to replace a vertebral body. When thus configured firststrut 262 and second strut 264 can have a height selected between about50 mm and 80 mm.

First strut 262 and second strut 264 interengage to provide an uppersurface 265 and a lower surface 267 that are substantially planar.Alternatively, assembled implant 260 can be adapted to exhibit an uppersurface 265 and lower surface that matingly engage and bear against theopposing endplates of vertebrae adjacent the implantation site. Forexample in alternative forms, implant 260 can exhibit a domed uppersurface 265 and/or lower surface 267 configured similar to the upper andlower surfaces of implant 240. Still further, implant 260 can exhibit alordotic configuration as illustrated for implant 290. Implant 260 canalso be described as providing a substantially cylindrical implantconfiguration. However, it is considered to be within the scope of thisinvention to provide implant 260 in a wide variety of configurations.Preferably implant 260 is provided in a shape resembling the nucleuspulposa. Other exemplary configurations include spherical, ovoidal,frustoconical, and kidney shaped.

FIGS. 17-19 illustrate another embodiment of an implant assemblyaccording to the present invention. Implant assembly 300 includes afirst bone-derived strut 302 and a second bone-derived strut 304. Eachof first strut 302 and second strut 204 includes pairs of oppositebone-engaging surfaces, 307, 309 and 311, 213, respectively. Implant 300also includes at least one, preferably two, cross-members 306 extendingbetween strut 302 and strut 304. An osteogenic material 310 isinterposed between first strut 302 and second strut 304.

First strut 302 and second strut 304 each define a curved wall 312 and314, respectively. Curved wall includes a first inner wall portion 316,which can be provided as a concave surface and an outer wall portion318, which can be provided as a convex surface. Similarly, second curvedwall portion strut 314 can also include an inner wall portion 320,provided as a concave surface and an outer wall portion 322 provided asa convex wall portion. In selected configurations, first and secondstruts 302 and 304 can be obtained from the diaphysis of long bones suchthat the respective concave surface portions are derived from and/orapproximate the medullary canal. Further, first and second struts 302and 304 can be provided with tool-engaging apertures 303 and 305,respectively. Implant 300 can be provided in a variety of dimensions foruse in the intervertebral space between adjacent vertebrae includingcervical vertebrae, thoracic vertebrae, and lumbar vertebrae.Preferably, first strut 302 and second strut 304 are spaced a distancefrom each other so that opposite pairs of bone-engaging surfaces 307,309 and 311, 213 bear against the peripheral ring apophysis of theadjacent vertebral bodies, as illustrated in FIG. 19.

As has been disclosed above, the illustrated embodiments of the implants10, 40, 70, 90A, 90B, 130, 160, 190, 240, 260, and 300 includecross-members. The cross-members are adapted to engage the respectivefirst and second struts of the respective implants. The cross-memberscan be, but are not required to be, secured to opposing struts with anadhesive. Examples of additional engaging portions and methods ofsecuring the cross-members to opposing struts are illustrated in FIGS.20-23.

In FIG. 20, cross-member 340 engages a groove such as dovetail slot 342formed in a first wall surface 343 of strut 344. In the illustratedembodiment, a dovetail portion 346 matingly engages in the dovetail slot342. For selected implant assemblies, for example, implant assemblies130, 160, 190 and 240, strut 342 can include a second dovetail slotformed on the opposite wall surface. When thus provided, strut 342 canengage in two or more struts that can extend through the implantassemblies. FIG. 21 illustrates an alternative embodiment for theengagement of an illustrative cross-member 350 with a strut 352.Cross-member 350 includes an end portion 354 that engages in an aperture356 formed in strut 352. In the illustrated embodiment, end portion 354includes external threads 355 provided to threadedly engage in athreaded portion 357 of aperture 356.

FIG. 22 illustrates another embodiment for an illustrative cross-member360 to engage in a strut 362. An end portion 364 of cross-member 360extends through an aperture 366 formed in strut 362. A retaining pin isreceived through a second opening 380 formed substantially orthogonal toaperture 366 in strut 362 and engages in end portion 364 of cross-member360 to inhibit withdrawal of the end portion 364 from aperture 366.

FIG. 23 illustrates a cross-member configured as a single substantiallyplanar structure. Cross-member 368 includes a tongue 369 adapted to bematingly received within a groove 373 formed in a first strut 371. Asecond strut 375 can provide a second groove 377 to receive a secondtongue on cross-member 368 opposite tongue 369.

FIGS. 24 and 25 illustrate still another embodiment of an engagement ofa cross-member 370 with a strut 372. End portion 374 of cross-member 370is received within an aperture 376 formed in strut 372. A retaining ring378 matingly engages in a groove 380 formed in end portion 374 thatextends beyond strut 372. This effectively inhibits withdrawal ofcross-member 370 from aperture 376 of strut 372.

Referring now to FIG. 26, there is illustrated a schematic of a boneslice 400 cut from a long bone, such as a tibia bone or a femur bone.Bone slice 400 can be cut along reference lines 404 and/or 406 toprovide a variety of bone-derived implants. For example, bone slice 400can be divided into a central section 402, which can be used as anintegrally formed implant potentially for insertion into adjacentvertebral bodies. Examples of integrally formed implants are describedin U.S. Pat. No. 5,972,368 issued to McKay and in U.S. Pat. No.5,033,438 issued to Bianchi. Bone portions 408 and 410, which remainafter harvesting central portion 402, can be used to provide a first,second or third strut for the implant assemblies according to thepresent invention. Furthermore, bone portions 408 and/or 410 can befurther partitioned to provide cross-members to extend from the firststrut to a second strut or from a second strut to a third strut. It willalso be observed that the illustrated bone portions 408 and 410 definefirst ends 412 and 414, respectively, that are thicker than the oppositesecond ends 416 and 418, respectively.

The osteogenic material is selected to adhere to the implant assembly.Further, osteogenic material preferably includes as a demineralized bonematrix and optionally a carrier, such as a gelatin substance. Thedemineralized bone matrix can be provided in the form of a powder, pasteor gel. When provided as a powder, the osteogenic material can bereconstituted with sterile water, saline, glycerin or otherphysiological solutions. The reconstituted material is molded about theimplant assembly. An osteogenic material can be applied to the implantassembly by the surgeon during surgery or the spacer assembly may besupplied with the composition pre-applied. In such cases, the osteogeniccomposition may be stabilized for transport and storage. Preferably theosteogenic material is provided as a putty that can be retained in andabout the implant assembly. The osteogenic putty is a moldable, flowablematerial that sets up to a semi-rigid form at about body temperature.The implant assembly with the osteogenic material is then inserted intoa prepared disc space. The osteogenic material can also include areinforcement such as bone chips, preferably cortical bone chips.Examples of osteogenic material suitable for use with this inventioninclude, but are not limited to: OSTEOFIL, which is commerciallyavailable from Regeneration Technologies, Inc. of Alachua, Fla.; GRAFTONCRUNCH available from Osteotech of Eatontown, N.J. and ALLOMATRIX,available from Allosource of Denver, Colo.

The term osteogenic composition used here means virtually any osteoconductive or osteo inductive material that promotes bone growth orhealing including natural, synthetic and recombinant proteins, hormonesand the like. The osteogenic materials used in this invention preferablycomprise a therapeutically effective amount of a bone inductive factorsuch as a bone morphogenetic protein in a pharmaceutically acceptablecarrier. Examples of factors include recombinant human bone morphogenicproteins (rhBMPs) rhBMP-2, rhBMP-4 and heterodimers thereof. However,any bone morphogenetic protein is contemplated including bonemorphogenetic proteins designated as BMP-1 through BMP-13, which areavailable from Genetics Institute, Inc., Cambridge, Mass. Allosteoinductive factors are contemplated whether obtained as above orisolated from bone.

The present invention contemplates modifications of the implant andmethods as would occur to those skilled in the art. It is alsocontemplated that processes embodied in the present invention can bealtered, rearranged, substituted, deleted, duplicated, combined, oradded to other processes as would occur to those skilled in the artwithout departing from the spirit of the present invention. Further itis understood that above described bone-derived components areindividual modular units that can be combined and/or assembled intoadditional configurations not specific illustrated in the figuresincluded herewith. All of the individual bone-derived components can beprovided in the varying sizes and include any of the specific surfacefeatures and structures associated with the embodiments illustrated ordescribed herein. In addition, the various stages, steps, procedures,techniques, phases, and operations within these processes may bealtered, rearranged, substituted, deleted, duplicated, or combined aswould occur to those skilled in the art. All publications, patents, andpatent applications cited in this specification are herein incorporatedby reference as if each individual publication, patent, or patentapplication was specifically and individually indicated to beincorporated by reference and set forth in its entirety herein.

Further, any theory of operation, proof, or finding stated herein ismeant to further enhance understanding of the present invention and isnot intended to make the scope of the present invention dependent uponsuch theory, proof, or finding.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same is considered to beillustrative and not restrictive in character, it is understood thatonly the preferred embodiments have been shown and described and thatall changes and modifications that come within the spirit of theinvention are desired to be protected.

1-36. (canceled)
 37. A method of treating a spinal deformity, saidmethod comprising: surgically preparing an intervertebral space betweenendplates of adjacent vertebrae; and impacting an implant comprising anassembly of cortical bone-derived components said components comprising:a first strut having a first bone-engaging portion, an opposite secondbone-engaging portion and a first impact surface disposed therebetween,a second strut spaced from said first strut, said second strut having athird bone-engaging portion, an opposite fourth bone-engaging portion,and a second impact surface disposed therebetween, said second strut incooperation with said first strut defining an internal space, and across-member extending from the first strut to the second strut into theintervertebral space.
 38. The method of claim 37 comprising impacting asecond implant adjacent to the first implant in the intervertebralspace.
 39. The method of claim 37 wherein said surgically preparing anintervertebral space includes performing a discectomy.
 40. The method ofclaim 37 comprising providing osteogenic material in the internal spaceof the implant.
 41. A method of treating a spinal deformity, said methodcomprising; surgically preparing a patent to receive a spinal implant;and impacting an implant comprising an assembly of cortical bone-derivedcomponents said components comprising: a first strut having a firstbone-engaging portion and a opposite second bone-engaging portion, saidfirst strut having first slot formed therein, and a second strut havinga third bone-engaging portion and a opposite fourth bone-engagingportion, said second strut interengaging said first strut to form theimplant.
 42. The method of claim 41 wherein said surgically preparing apatent to receive an implant includes performing a discectomy.
 43. Themethod of claim 41 wherein said surgically preparing a patent to receivean implant includes removing a vertebra.
 44. The method of claim 41comprising providing an osteogenic material with the implant.
 45. Amethod of treating a spinal deformity, said method comprising:surgically preparing an intervertebral space; and inserting an implantcomprising an assembly of cortical bone-derived components saidcomponents comprising: a first strut including a substantially planar,first exterior surface, a first insertion end orthogonal to the firstexterior surface, and an opposite, first tool engaging end having anaperture sized to engage an insertion tool therein, and a second strutincluding a substantially planar, second exterior surface, a secondinsertion end orthogonal to the second external surface, and anopposite, second tool engaging end having an aperture sized to engagethe insertion tool therein, said second strut in cooperation with saidfirst strut defining an internal space, and a cross-member extendingthrough the internal space and securing the first strut to the secondstrut.
 46. The method of claim 45 comprising inserting a second implantinto the intervertebral space.
 47. The method of claim 45 wherein saidsurgically preparing an intervertebral space includes performing adiscectomy.
 48. The method of claim 45 comprising providing osteogenicmaterial in the internal space of the implant.
 49. The method of claim45 comprising adding an osteogenic material to the internal space. 50.The method of claim 45 wherein the first and second insertion endsinclude curved surfaces configured to facilitate insertion of theimplant into the prepared intervertebral space.
 51. The method of claim45 wherein the first and second struts are trapezoid shaped.